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Abstract
The incidence of spontaneous anomalies and other aspects of reproduction in mice from the Upj:TUC(ICR)spf strain were studied to enhance the utility of these mice for teratology studies. Fetuses were examined from mice in the following test groups: unhandled and untreated, untreated but weighed on gestation d 6–15, treated orally with 0.25% methylcellulose vehicle on gestation d 6–15, treated orally with sterile water on gestation d 6–15, treated orally with 20 mg/kg cyclophosphamide on gestation d 10, and treated orally with 2.5 mg/kg hydrocortisone on gestation d 11–14. Each test group (except hydrocortisone) had a minimum of 25 pregnant dams. The incidence of anomalies in fetuses from dams that were weighed or weighed and treated with vehicles (5.4%) was comparable to that in fetuses from dams that were neither handled nor treated (6.8%). The most common anomalies were cleft palate, talipes, left umbilical artery, and sternebral changes. The most frequent skeletal variations were cervical ribs, accessory (lumbar) ribs, and combinations thereof. With the exception of dams given cyclophosphamide, no statistically significant increase in numbers of resorption sites or decrease in numbers of live fetuses or maternal or fetal body weights occurred in any test group. The TUC(ICR) mouse was sensitive to cyclophosphamide and hydrocortisone. Of fetuses from dams given cyclophosphamide, 95% were malformed. The incidence of cleft palate in the untreated and vehicle‐treated groups was 1.2%; however, 33.3% of the fetuses from dams given hydrocortisone had cleft palates, and this difference was highly significant.